In the field of well stimulation it is known to use a tool of elongated shape, adapted to being inserted into a well.
Such a tool comprises a first electrode and a second electrode, electrically insulated from each other, extending substantially from one end to the other of said tool. Said first and second electrodes form a stimulation head in the area of one end of the tool. The stimulation head generally comprises a chamber designed to receive a fluid, into which said first and second electrodes emerge. Examples of the realization of such a tool are known:                from U.S. Pat. No. 4,345,650, which describes a tool implemented to improve the production of a well for extraction of underground resources,        from international patent application WO9013830, which describes a tool implemented to perform a seismological study,        from U.S. Pat. No. 4,479,680, which describes a tool implemented to perform a fracturing of underground rock.        
During stimulation operations, the tool is inserted into a well with the stimulation head toward the bottom, and it is lowered to the point where the stimulation needs to be performed. Once the stimulation point has been reached, pulses of high-intensity electric current (able to exceed several dozen kilo-amperes) are sent into the first electrode. A current arc is then formed in the chamber of the stimulation head between the first electrode and the second electrode (generally connected to the electrical ground). Said current arc enables the forming of a shock wave which will stimulate the well. For example, such a shock wave may enable an unclogging of the perforations of an extraction well.
In the fields of oil and gas, the boreholes are generally for the most part straight, such as vertical or horizontal, but they can also be nonstraight, for example, to get around an obstacle or reach a layer of hydrocarbon.
From patent application US 2001/011590 A1 there is known a stimulation tool to be inserted into a borehole, comprising several segments joined by articulated links enabling local bending of said stimulation tool. Thanks to these articulated links, such a stimulation tool can be inserted into a nonstraight borehole. However, owing to the high levels of voltage and current needed to generate a shock wave, there is a not insignificant risk of forming electric arcs inside the stimulation tool and/or in the area of the articulated link.